An optical MUX is a device that receives multiple optical signals of multiple respective wavelengths being carried on multiple respective optical channels and combines them onto a single optical channel. Optical MUXes have a variety of uses, one of which is to perform wavelength division multiplexing (WDM) in optical communications networks. Optical MUXes may be located at various nodes of the network for MUXing multiple optical signals of different wavelengths onto a single optical waveguide, which is typically an optical fiber. An optical demultiplexer (DeMUX) performs optical operations that are the opposite of those performed by an optical MUX. An optical DeMUX receives multiple optical signals of multiple respective wavelengths being carried on a single optical channel and separates them out onto multiple respective optical channels. Thus, an optical DeMUX performs wavelength division demultiplexing operations.
There are several ways to build an optical MUX or DeMUX. Optical MUXes and DeMUXes may be built of bulk optical components or integrated optical elements. Integrated optic systems such as photonic logic circuits (PLCs) use diffractive (Echelle) gratings and arrayed waveguides (AWGs) to perform the optical multiplexing and demultiplexing operations. Similarly, wavelength-selective optical filters and optical reflectors may be used to perform the optical multiplexing and demultiplexing operations.
In order to ensure that the optical MUXing and DeMuxing operations are performed with high performance (low insertion loss when coupled through singlemode fibers), the optical elements must be constructed with very high dimensional and positional precision, especially in the MUX assembly, which requires that there be very tight dimensional control over the manufacturing process. To date, such tight dimensional control has not been consistently achieved. The industry relies on active alignment of the components in the individual channels to achieve the performance required.
Accordingly, a need exists for an optical MUX and an optical DeMUX that can be manufactured with high precision using existing manufacturing technologies.